IDAX and MIDAX printing techniques are commercial electrographic imaging processes that utilize what is referred to as "silent electric discharge". In such systems, an ion cartridge is mounted adjacent an imaging drum. The drum then moves into contact with the transfer sheet (for example, paper). Conventional cartridges utilized in these printing systems include first and second electrodes, typically called the drive and control electrodes, separated by a solid dielectric member such as a sheet of mica. The control electrode, typically in the form of control fingers, defines an edge surface disposed opposite the driver electrode to define a discharge region at the junction of an edge surface in the solid dielectric member. An alternating potential is applied between the driver and control electrodes of sufficient magnitude to induce charged particle producing electrical discharges in the discharge region, and means are provided for applying a charged particle extraction potential between the control electrode and a further electrode, so that imaging occurs on the imaging drum, or paper or like dielectric moving past the ion cartridge. In most commercial installations, a screen electrode is also provided between the imaging drum and the control electrode, and separated by an insulating spacer from the control electrode. A commercial ion cartridge is typically constructed of a plurality of driver, control, and screen electrode units, in a matrix form. Conventional ion cartridges are disclosed in U.S. Pat. Nos. 4,155,093; 4,160,257; 4,267,556; and 4,381,327.
A toning station for supplying toner particles to the imaging cylinder is also provided to create a visible counterpart of the latent electrostatic image. Typically, a transfer roller is employed in rolling contact with the imaging cylinder under high pressure to transfer and simultaneously fuse the toner particles to a paper or other receptor sheet.
Laboratory and in-plant tests indicate the need for improved cleaning of the imaging cylinder and toner released to the paper within the print engine, particularly when color toners are employed. The primary problem relates to the presence of banded deposits around the imaging cylinder, the composition of which includes conductive powder that is attached to the toner particles to increase their electrical conductivity. This powder, a heavy metal tin/antimony oxide (known as T1), deposits itself in a very thin film on the surface of the imaging cylinder and is not removed by existing scraper and brush cleaning assemblies. The use of solvents has also proven ineffective against the deposited scum. It has been discovered that one effective way to clean the bands is by running hundreds of feet of plain paper through the machine to scour off the scum, but this is impractical in day-to-day operation.
This invention relates to a method and apparatus for solving the problem of scum deposits on the imaging cylinder. In the exemplary embodiment, the invention incorporates into an IDAX or MIDAX type machine the following components and/or manipulative steps: (1) A scraper blade with an improved swivel and spring mounting for better drum following and improved distribution of forces to assure a non-stressed flat loading on the scraper blade; (2) Direct air purging of the area around the scraper blade to assure removal of scraped powders; (3) A silicone impregnated, continuous cleaning web which is held tightly against the imaging cylinder (downstream of the scraper blade) with a resilient roller, spring loaded for better distribution of forces, driven at a slow rate in a direction counter to the direction of the imaging cylinder, and controlled in speed and tension with simple but effective mechanical controlling mechanisms; (4) A two-piece housing assembly, the bottom or lower portion of which serves as an assembly base and plenum chamber and carries the scraper and vacuum channels, while the top or upper portion carries the cleaning web, drive and tensioning assemblies.
In its broader aspects, therefore, the present invention provides cleaning apparatus for an imaging cylinder in an ion deposition printer comprising a scraper blade having an edge engaging the imaging cylinder; and a continuous cleaning web engaging the imaging cylinder downstream of the scraper blade, the cleaning web impregnated with silicone oil.
In another aspect, the present invention relates to a cleaning apparatus for an imaging cylinder in an ion deposition printer comprising a housing having an upper portion and a lower portion separated by an internal plate, the lower portion comprising a plenum chamber having an opening at one end and a vacuum port at an opposite end; a scraper blade mounted in the lower portion and having an edge engaging the imaging cylinder; and a continuous cleaning web mounted in said upper portion engaging the imaging cylinder downstream of the scraper blade, the cleaning web being impregnated with oil.
In still another aspect, the present invention relates to a method of cleaning toner and conductive powder deposits from an ion deposition printer imaging cylinder comprising the steps of:
a) engaging a peripheral surface of the imaging cylinder with a scraper blade to remove toner particles therefrom; and
b) engaging the peripheral surface of the imaging cylinder downstream of the scraper blade with a continuous web impregnated with oil to remove residual toner particles and conductive powder deposits.
It has been found that the scraping blade removes most of the toner from the imaging cylinder, and that the silicone impregnated web scours and entrains the residual toner as it engages the imaging cylinder, thereby giving a cleaner performance to the remainder of the machine components. The web also scours and entrains separated heavy metal oxides present from the color toner formulation and thereby prevents the buildup of the conductive scum on the imaging cylinder which otherwise may cause premature image fading. The silicone oil from the web has been found to form a thin release layer which may assist in toner transfer to the paper while decreasing the amount of residual toner which could otherwise foul the system. The deposited silicone oil can also transfer to intermediate transfer members thus helping the transfer efficiency of the toner to the paper.
Other objects of the invention will become apparent from the detailed description which follows.